Cormorants and Otters – Pond Predators

If you ask lake managers and fish farmers to name dreaded predators that severely damage fisheries, most will say double-crested cormorants (water turkey) and otters.

Double-crested Cormorant Phalacrocorax auritus, Humber Bay Park (Toronto, Canada). Courtesy of Wikipedia.

Cormorants are found from southern Alaska to Mexico. They have dark plumage and a body length two to three feet. Webbed feet make them excellent swimmers. They eat primarily fish and hunt by swimming and diving. Cormorants may dive five to 25 feet for 30 to 70 seconds. Smaller fish may be consumed beneath the surface. Larger prey often is brought to the surface before eaten.

This efficient predator is an opportunistic hunter. It typically catches two to six-inch fish of any species and may eat a pound or more daily. Scout birds locate prospective feeding grounds and return with large flocks. It’s not uncommon to see 20 or more than 100 depending on lake size. They can significantly damage a bass forage base in a matter of days. Fish suppliers in Arkansas tell stories of entire hatchery ponds being wiped-out. If you’ve noticed a long scratch on a fish during winter or early spring, it may have been caused by a cormorant’s sharp beak.

Since feathers are not fully waterproof, they spend long periods with wings extended to dry feathers. Average life span is six years. Once threatened by DDT, the chemical was banned. Since the product was discontinued, numbers have increased dramatically. Population gains are attributed to feeding opportunities at aquaculture ponds in southern wintering grounds. In flight, they develop a v-formation resembling a flock of geese. You can recognize them from longer tails. Geese have short, stubby tails.

We encourage you monitor cormorant traffic and devise a management plan to discourage visitation. They’re bold critters. You can chase them away in the morning. They may return the same day. Like most migratory species, cormorants are regulated by the U.S. Fish and Wildlife Service. There is no hunting season. If you feel cormorants threaten the viability of your lake, contact local game wardens or the U.S. Fish and Wildlife Service for predation permits and management options.

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Otters rank as a villain next to cormorants. They often travel with family groups and damage fish populations, especially in small ponds. Otter are the largest furry cousin of the weasel family. Their body shape is slim. Average length is three to five feet. Approximate weight is 15 to 30 pounds. A flat tail about one-third its body length makes them excellent swimmers.

Otters hunt by diving and chasing fish. They may remain under water four minutes and dive 60 feet. Favored habitats are abandoned beaver huts. They’re nocturnal and travel via creeks and rivers. Watch for partially eaten fish carcasses on the shoreline. Monitor worn paths from a creek, up the back of a dam, and into the pond. Look for scat containing fish scales or crayfish remnants. Scat piles are scent posts and may be large from multiple visits. If you require services of a professional trapper, contact county extension or Natural Resource Conservation Service agents for referrals.